The invention relates to a transdermal therapeutic system for the treatment of Parkinson's syndrome, comprising a backing layer which is inert to the ingredients of the matrix, a self-adhesive matrix layer containing (−)-5,6,7,8-tetrahydro-6-[propyl-[2-(2-thienyl)ethyl]amino]-1-naphthalenol having the below-indicated formula
in an effective amount, and a protective layer which is to be removed prior to use.
Worldwide about 2.5-3% of the population suffer from so-called Parkinson's syndrome, which breaks out mainly at the age between 58 and 62. The symptoms of this disease manifest themselves in motorial disorders such as trembling, muscle stiffening, vegetative disorders such as increased flow of saliva and tears, disturbed thermoregulation, hypopiesia and functional disorders of bladder and intestine, as well as psychic disorders such as irresoluteness and depressive mood.
Parkinson's syndrome is caused by the degeneration of dopaminergic neurons in the substantia nigra. This leads to the depletion of dopamine in certain cerebral regions, in particular in the brain stem ganglia. The resultant disturbed balance between the neurotransmitters acetylcholine and dopamine is in the end responsible for the symptoms of the disease. A predominance of acetylcholine is responsible for the so-called plus symptoms, and a deficiency of dopamine is responsible for the so-called minus symptoms.
Parkinson's syndrome can therefore be treated with so-called anticholinergics or levodopa. Anticholinergics impede the cholinergic neurotransmission, and levodopa passes, as precursor of dopamine, the blood-brain barrier and is converted in the brain to dopamine.
Another path of treatment of Parkinson's syndrome is the treatment with dopamine receptor agonists. Dopamine agonists are substances which, although structurally different from dopamine, bind to the same receptors and trigger an effect similar to that of dopamine. Due to their molecular structure dopamine receptor agonists have properties which enable them to overcome the blood-brain barrier. In this connection it is advantageous if the substances bind selectively to a subgroup of the dopamine receptors, the D2-receptors, as this decreases side effects. In this connection, the substance (−)-5,6,7,8 tetrahydro-6-[propyl-[2-(2-thienyl)ethyl]amino]-1-naphthalenol having the above-indicated formula, has proved an especially effective selective D2-agonist.
Due to this compound's half-life and high first-pass effect, oral administration of this substance is, however, very problematic. The short half-life would necessitate frequent intake of the substance, and the high first-pass effect would necessitate high dosage. Whereas the intake frequency may possibly be overcome by an appropriate oral formulation, the problem of high first-pass effect can be solved in principal only by a non-oral administration of the active substance.
A transdermal system designed for the administration of a D2-agonist of the above-indicated formula has already been described in WO 94/07468. This system contains the active substance as hydrochloride in a two-phase matrix which is formed substantially by a hydrophobic polymer material, which is present as a continuous phase, with hydrated silicate dispersed therein for taking up the hydrophilic drug salt, and additionally contains, or may contain, hydrophobic solvents, permeation-enhancing agents and dispersing agents.
This system has the disadvantage that the active substance salt must be mixed with the silicate in aqueous solution, and that an additional emulsifier is necessary to emulsify this aqueous solution with the lipophilic polymer, which is dissolved in an organic solvent—commonly hexane, heptane or ethyl acetate. Due to coating problems, it is much more difficult to manufacture transdermal systems using this emulsion. In addition, for such systems only the salt can be used, since only the salt is sufficiently hydrophilic to be soluble in water.
It is thus the object of the invention to develop systems for (−)-5,6,7,8-tetrahydro-6-[propyl-[2-(2-thienyl)ethyl]amino]-1-naphthalenol avoiding the disadvantages of the system described in WO 94/07468.
In this connection, the invention particularly focuses on optimizing active substance uptake within the system, and skin transfer.